Fixes #20810

Change-Id: I09365b2db50c41aa3383dd730859b6f2cdb78e63
Reviewed-on: https://go-review.googlesource.com/46836
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>